A backlight module belongs to a kind of a backlight assembly. Particularly in a direct-type backlight module, a diffusion sheet is required to be disposed in the backlight module, so as to make the backlight module supply uniform light.
For example, a diffusion sheet in a backlight module mainly includes a light-transmissive sheet-like substrate with surfaces on its two sides, on which a plurality of spherical particles is uniformly distributed. The spherical particles are different in light transmission and refraction coefficient from the substrate. The periphery surfaces of the spherical particles are uniformly encapsulated with a surface coating layer that is different in light-transmission and refraction coefficient from both the substrate and the spherical particles. Light can be refracted many times by the substrate, the spherical particles and the surface coating layer in a process of passing through the diffusion sheet, so as to produce a uniform diffusing effect.